What are the hammer anvil & stirrup parts of?

Jane EllisUpdated April 17, 2017

The hammer, anvil and stirrup are the common English terms for three bones in the ear and are part of the auditory system. Respectively, the proper terms for these three bones are the malleus, incus and stapes. The hammer, anvil and stirrup, which are the tiniest bones in the human body, make up a part of the middle ear known as the ossicles.

The Hammer, Anvil and Stirrup are Parts of the Inner Ear

The human ear is made up of three main parts, the outer ear, the inner ear and the middle ear. Humans hear things by first picking up sound waves through the outer ear. These waves then enter the ear canal and reach the eardrum, which is at the entrance of the middle ear. Inside of the middle ear are the three tiny bones known as the hammer, anvil and stirrup, which work together to transfer the vibrations to the inner ear.

How These Bones Work

When sound waves hit the eardrum, it starts to vibrate. The eardrum passes these vibrations onto the small hammer bone. The anvil, which touches the hammer, then picks up the vibrations and sends them onto the stirrup bone. Finally, the stirrup passes the vibrations out of the middle ear to a liquid-filled sack in the inner ear. Tiny structures in the inner ear called hair cells pick up the signals, and they in turn send on electric signals to the brain through the auditory nerve, which eventually processes as sound.

What Can Damage the Hammer, Anvil and Stirrup?

If the hammer, anvil and stirrup are damaged, it could cause permanent hearing loss. Damaged ossicles can be caused by a genetic disorder, a physical trauma to the middle ear, a bad concussion, or a serious infection. While most ear infections will have no permanent negative effects, a severe one left untreated could possibly damage these small bones. Objects that puncture the eardrum could also damage the hammer, anvil or stirrup. A bad concussion can also disrupt the way these bones and the eardrum work together, which may also lead to permanent hearing loss.

Care and Repair of the Hammer, Anvil and Stirrup

To prevent damage to the hammer, anvil and stirrup, don't put objects, especially sharp ones, into an ear, as they may rupture the eardrum and potentially harm these tiny bones. Someone suffering from a severe ear infection should see a doctor quickly and not wait for an injury to heal on its own.

If a person suffers from a hereditary defect of these bones, he may be able to have it surgically repaired. For instance, in one such condition, known as otosclerosis, the hammer, anvil and stirrup do not grow correctly and eventually stop transmitting vibrations to the inner ear. To cure this condition, a surgeon can replace the stirrup with an artificial one.